Timothy L. Hooper

Mitral repair best practice: proposed standards

Objectives: To define best practice standards for mitral valve repair surgery. Design: Development of standards for process and outcome by consensus. Setting: Multidisciplinary panel of surgeons, anaesthetists, and cardiologists with interests and expertise in caring for patients with severe mitral regurgitation. Main outcome measures: Standards for best practice were defined including the full spectrum of multidisciplinary aspects of care. Results: 19 criteria for best practice were defined including recommendations on surgical training, intraoperative transoesophageal echocardiography, surgery for atrial fibrillation, audit, and cardiology and imaging issues. Conclusions: Standards for best practice in mitral valve repair were defined by multidisciplinary consensus. This study gives centres undertaking mitral valve repair an opportunity to benchmark their care against agreed standards that are challenging but achievable. Working towards these standards should act as a stimulus towards improvements in care.

Predicting operative risk for coronary artery surgery in the United Kingdom: a comparison of various risk prediction algorithms

Objective To compare the ability of four risk models to predict operative mortality after coronary artery bypass graft surgery (CABG) in the United Kingdom. Design Prospective study. Setting Two cardiothoracic centres in the United Kingdom. Subjects 1774 patients having CABG. Main outcome measures Risk factors were recorded for all patients, along with in-hospital mortality. Predicted mortality was derived from the American Society of Thoracic Surgeons (STS) risk program, Ontario Province risk score (PACCN), Parsonnet score, and the UK Society of Cardiothoracic Surgeons risk algorithm. Results There were significant differences (p < 0.05) between the British and American populations from which the STS risk algorithm was derived with respect to most variables. The observed mortality in the British population was 3.7% (65 of 1774). The mean pre- dicted mortality by STS score, PACCN, Parsonnet score, and UK algorithms were 1.1%, 1.6%, 4.6%, and 4.7% respectively. The overall predictive ability of the models as measured by the area under the receiver operating characteristic curve were 0.64, 0.60, 0.73, and 0.75, respectively. Conclusions There are differences between the British and American populations for CABG and the North American algorithms are not useful for predicting mortality in the United Kingdom. The UK Society of Cardiothoracic Surgeons algorithm is the best of the models tested but still only has limited predictive ability. Great care must be exercised when using methods of this type for comparisons of units and surgeons.

Critical importance of the first 10 minutes of lung graft reperfusion after hypothermic storage

BACKGROUND We have shown previously that lung graft function can be improved by achieving reperfusion with stepwise increments of perfusion pressure over 60 minutes. This study aimed to establish whether similar benefit could be achieved with a shorter, simpler protocol and different storage conditions. METHODS Rat lungs were flushed with University of Wisconsin or modified Euro-Collins solution and reperfused for 1 hour with blood from a support animal. Grafts were reperfused immediately or after storage at 4 degrees C for 24 hours (University of Wisconsin solution) or 6 hours (Euro-Collins solution). Stored-graft reperfusion was initiated with a 0-, 5-, or 10-minute period during which reperfusion pressure was reduced by 50%. RESULTS Stored grafts receiving 0 to 5 minutes of initial low-pressure reperfusion performed poorly, with reduced oxygenation and blood flow and elevated pulmonary artery pressure, airway pressure, and wet/dry weight ratio. In contrast, 10 minutes of initial 50%-pressure reperfusion yielded function comparable with that in controls with both storage conditions. CONCLUSIONS An initial 10-minute period of 50%-pressure reperfusion improves the function of stored rat lung grafts, whereas 5 minutes is insufficient.

Controlled Reperfusion Protects Lung Grafts During a Transient Early Increase in Permeability

BACKGROUND We have previously shown that an initial 10-minute period of low-pressure reperfusion prevents the lung graft dysfunction that follows physiologic-pressure reperfusion. Possible mechanisms were investigated in this study. METHODS Rat lungs were reperfused ex vivo using a parabiotic animal after 0-hour (groups A through C) or 24-hour (groups D through G) storage. Reperfusion pressure was either physiologic (groups A through D) or reduced by 50% for a specified time (groups E through G). The duration of reperfusion was 5 minutes (groups A, D, and E), 10 minutes (groups B and F), or 30 minutes (groups C and G), at which time endothelial permeability was measured through iodine 125-labeled albumin leakage and neutrophil sequestration through tissue myeloperoxidase activity. RESULTS Graft function in group D deteriorated rapidly, whereas groups E through G performed at control levels. Albumin leakage was significantly elevated in group D; with controlled reperfusion, it was elevated after 5 minutes (group E) but had returned to baseline at 10 minutes (group F) and 30 minutes (group G). Myeloperoxidase levels were not significantly different between groups. CONCLUSIONS Endothelial permeability is transiently elevated in the early phase of lung graft reperfusion. Initial low-pressure reperfusion may be protective by preventing irreversible edema formation during this period.

A method for the morphological analysis of the regurgitant mitral valve using three dimensional echocardiography

Background: Atrial en-face reconstructions are commonly used to assess mitral valve morphology in three dimensional (3D) echocardiography but may miss important abnormalities. Objective: To present a systematic method for the analysis of the regurgitant mitral valve using a combination of en-face and longitudinal views for better anatomical evaluation. Methods: Detailed 3D assessment was done on 58 patients undergoing mitral valve repair. En-face and longitudinal views were compared for detection and location of primary pathology. The quality of acquisitions under general anaesthesia and sedation was also compared. Results: Recognition of valve structure was significantly better with longitudinal reconstruction for both mitral leaflets but not for the commissures. Accurate identification of pathology was possible in 95% cases, compared with 50% for en-face reconstruction (p < 0.001). There was no significant difference between imaging under sedation and anaesthesia. Conclusion: En-face reconstructions alone are inadequate. Additional longitudinal reconstructions are necessary to ensure full inspection of valve morphology.

Low-Dose Nitric Oxide Inhalation During Initial Reperfusion Enhances Rat Lung Graft Function

BACKGROUND In ischemia-reperfusion injury, the production of nitric oxide by dysfunctional endothelium falls rapidly within minutes of the onset of reperfusion. Replenishment during this critical early period using inhaled nitric oxide may benefit lung grafts through modulation of vascular tone, endothelial permeability, neutrophil and platelet function, and availability of reactive oxygen species. METHODS Rat lung grafts were flushed with 60 mL/kg cold University of Wisconsin solution and were reperfused either immediately (group I, n = 5) or after 24-hour 4 degrees C storage (groups II and III, n = 5 each), for 60 minutes in an ex vivo model incorporating a support animal. Graft ventilation was with room air. In group III, 20 parts per million inhaled nitric oxide was added during the initial 10 minutes of reperfusion, whereas in groups I and II, equivalent flows of nitrogen were added to standardize oxygen concentration. RESULTS Compared with group I, graft function in group II was poor, with reductions in oxygenation and blood flow and elevations of mean pulmonary artery pressure, peak airway pressure, and wet to dry weight ratio. In contrast, during nitric oxide inhalation in group III, graft function improved to control levels. This improvement was subsequently sustained throughout the reperfusion period. CONCLUSIONS Low-dose inhaled nitric oxide administration in the early phase of reperfusion of stored lung grafts can yield sustained improvement in function. There may be a role for inhaled nitric oxide in the prevention of reperfusion injury in transplanted lungs.

Skeletal muscle ventricles as left atrial-aortic pumps: short-term studies.

In 5 dogs, skeletal muscle ventricles (SMVs) were constructed from the latissimus dorsi muscle and placed in the left hemithorax. After a 3-week vascular delay period, SMVs were electrically preconditioned with 2-Hz stimulation for 6 weeks. At a second operation, SMVs were connected between the left atrium and thoracic aorta by afferent and efferent aortic root homografts, and stimulated to contract in a 1:2 diastolic mode. At a mean left atrial pressure of 12.4 +/- 1.3 mm Hg and a burst stimulation frequency of 33 Hz, SMV stroke volume was initially 43% of that of the native left ventricle, achieving a flow equivalent to 21% of cardiac output (194 +/- 38 versus 902 +/- 85 mL/min). At 50-Hz stimulation, this figure rose to 27% (246 +/- 41 mL/min; p less than 0.05). Skeletal muscle ventricle power output (the product of stroke work and contraction rate) at 33 Hz was 0.016 +/- 0.003 W, increasing to 0.024 +/- 0.004 W at 50 Hz (p less than 0.05), corresponding to 14% and 22%, respectively, of left ventricular power output (0.11 +/- 0.012 W). After 4 hours of continuous pumping, four of the SMVs were still generating flows of more than 70% of starting values and more than 60% of initial power output. This study demonstrates that SMVs can function in the systemic circulation at physiologic left atrial preloads.

Minimally invasive aortic valve replacement through a transverse sternotomy: a word of caution

Objectives To compare aortic valve replacement (AVR) using a minimally invasive approach through a transverse sternotomy with the established approach of median sternotomy. Design Retrospective, case-control study. Patients Fourteen high risk patients (median age 78, Parsonnet score of 18%) who underwent AVR performed through a minimally invasive transverse sternotomy were compared with a historical group of patients matched for age, sex, and Parsonnet score who underwent AVR performed through a median sternotomy by the same surgeon. Outcome measures Cross clamp time, total bypass time, intensive care stay, postoperative in-hospital stay, morbidity, and mortality. Results There were two deaths in the minimally invasive group and none in the control group (NS). The cross clamp and total bypass times were longer in the minimally invasive group (67 and 92 minutes v 46 and 66 minutes, p < 0.001). There was a higher incidence of re-exploration for bleeding (14% v0%) and paravalvar leaks (21% v 0%) in the minimally invasive group but these differences were not significant. The minimally invasive group had a longer postoperative in-hospital stay (p = 0.025). The incidence of mortality or major morbidity was 43% (six of 14) in the minimally invasive group and 7% (one of 14) in the matched pairs (p = 0.013). Conclusions AVR can be performed through a transverse sternotomy but the operation takes longer and there is an unacceptably high incidence of morbidity and mortality.

Attenuation of lung graft reperfusion injury by a nitric oxide donor

OBJECTIVE One of the primary features of ischemia-reperfusion injury is reduced production of protective autocoids, such as nitric oxide, by dysfunctional endothelium. Administration of a nitric oxide donor during reperfusion of lung grafts may therefore be beneficial through modulation of vascular tone and leukocyte and platelet function. METHODS Rat lung grafts were flushed with University of Wisconsin solution and reperfused for 1 hour in an ex vivo model incorporating a support animal. Group I grafts (n = 6) were reperfused immediately after explantation, group II (n = 6) and III (n = 5) grafts after 24 hours of storage at 4 degrees C. In group III, glyceryl trinitrate, a nitric oxide donor, was administered during the first 10 minutes of reperfusion at a rate of 200 micrograms/min. In an additional group (n = 5), 200 micrograms/min hydralazine was administered instead, to assess the effect of vasodilation alone. RESULTS Graft function in group II deteriorated compared with that in group I, with significant reduction of graft effluent oxygen tension and blood flow and elevation of pulmonary artery pressure, peak airway pressure, and wet/dry weight ratio. In contrast, in group III, glyceryl trinitrate treatment improved graft function to baseline levels in all these parameters. Administration of hydralazine, meanwhile, produced mixed results with only two out of five grafts functioning at control levels. CONCLUSIONS In this model, administration of glyceryl trinitrate to supplement the nitric oxide pathway in the early phase of reperfusion has a sustained beneficial effect on lung graft function after 24-hour hypothermic storage, probably through mechanisms beyond vasodilation alone.

A regional survey of chest drains: evidence-based practice?

Although the use of chest drains is common in medicine, there appear to be wide variations in practice. A survey was therefore conducted to establish the current status of chest drain management in the Northwest region. A questionnaire targeted consultants practising in the specialties of chest medicine, general surgery, accident & emergency and cardiothoracic surgery. The questionnaire consisted of five sections encompassing aspects of the insertion, day-to-day care and removal of chest drains. With an overall response rate of 75.3% (110/146), important variations in every major aspect of the practice of chest drains were found between the specialties and to a large extent within each specialty. We have made a number of recommendations which aim to encourage good practice and reduce unnecessary complications, including the adoption of standardised protocols for inserting and managing chest drains.